CVE-2026-50355: Microsoft Active Directory Federation Services stack buffer overflow

CVE-2026-50355 · Severity: high · CVSS 7.5 · Published 2026-07-14

A security vulnerability exists in Microsoft's Active Directory Federation Services (AD FS), a component used to provide single sign-on access to systems and applications. An unauthorized attacker can exploit this flaw over the network to crash the service, preventing legitimate users from logging into their corporate accounts and applications. This results in a significant disruption to business operations and identity management services.

Technologies: Microsoft Active Directory Federation Services, Microsoft Windows Server 2012 R2, Microsoft Windows 10, Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019. Vendors: Microsoft.

Quick answers

Is CVE-2026-50355 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-50355 being exploited in the wild.
How severe is CVE-2026-50355?
High severity, with a CVSS score of 7.5, published 14 July 2026.
Which products and versions are affected?
Microsoft Windows 10 Multiple versions prior to July 2026 updates; Microsoft Windows Server 2012 Multiple versions prior to July 2026 updates.
Is there a fix for CVE-2026-50355?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-50355 attacked?
It is attacked over the network, in an operating system.
Am I affected by CVE-2026-50355?
Check whether you run Microsoft Active Directory Federation Services, Microsoft Windows Server 2012 R2, Microsoft Windows 10 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A stack-based buffer overflow (CWE-121) exists in Microsoft Active Directory Federation Services (AD FS). The vulnerability is reachable over the network without authentication (AV:N/AC:L/PR:N/UI:N). By sending specially crafted requests to the AD FS endpoint, an attacker can trigger the overflow to crash the service, leading to a denial-of-service (DoS) condition. While the primary impact is availability, stack overflows can sometimes lead to remote code execution, though Microsoft has classified this specific instance as a DoS. Security updates were released in July 2026 to address this issue across affected Windows and Windows Server versions.

Affected products

  • Microsoft Windows 10 Version 1607 / 1809 Multiple versions prior to July 2026 updates
  • Microsoft Windows Server 2012 / 2012 R2 / 2016 / 2019 Multiple versions prior to July 2026 updates
  • Microsoft Active Directory Federation Services (AD FS)

Timeline

  • 2026-07-14: disclosed
  • 2026-07-14: advisory

References

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